JP2901705B2 - Semiconductor substrate cleaning method - Google Patents

Description

The present invention relates to a method for cleaning a semiconductor substrate, and more particularly to an improvement in a cleaning method using a plurality of cleaning liquids.

(Prior Art) As is well known, the degree of integration of a semiconductor device is very high depending on the cleanliness of a semiconductor substrate. Therefore, the demand for a method of cleaning a semiconductor substrate has recently become higher.

Under such circumstances, a method which is conventionally called a so-called batch method will be described below with reference to the drawings.

FIG. 2 is a cross-sectional view showing the first method, and a cleaning method using two types of cleaning liquids will be described with reference to FIG.

Reference numeral 1 denotes a washing tank, at the bottom of which a discharge pipe 2 is provided with a discharge valve 3.
Is provided in the middle portion, and a shelf 5 having a plurality of holes 4 through which the cleaning liquid flows is provided in the middle portion from the bottom surface to the top surface. The shelf 5 is provided at a position where the semiconductor substrate 7 as an object to be cleaned placed on the substrate transporter 6 is below the level of the cleaning liquid. A supply pipe 9 provided with a supply valve 8 for supplying the cleaning liquid A into the cleaning tank 1 is disposed above the cleaning tank 1, and a supply valve 10 for supplying the cleaning liquid B is provided at the bottom of the cleaning tank 1. The provided supply pipe 11 is attached.

In such a configuration, the semiconductor substrate 7 is placed on the shelf 5 of the cleaning tank 1 while being placed on the substrate transporter 6, the discharge valve 3 is closed, the supply valve 8 is opened, and the cleaning is performed from the supply pipe 9. The cleaning liquid A is supplied to the tank 1. Cleaning liquid A is applied to semiconductor substrate 7
Is filled in the washing tank 1 until the entire surface is soaked, the supply valve 8 is closed, and washing is performed for a predetermined time. Thereafter, the discharge valve 3 is opened, and the cleaning liquid A in the cleaning tank 1 is discharged via the discharge pipe 2. Subsequently, the discharge valve 3 is closed, the supply valve 10 is opened, and the cleaning liquid B is supplied from the supply pipe 11 to the cleaning tank 1. The cleaning tank 1 is filled with the cleaning liquid B in the same manner as the cleaning liquid A until the entire surface of the semiconductor substrate 7 is immersed,
The supply valve 10 is closed and cleaning is performed for a predetermined time. Then, the discharge valve 3 is opened, the cleaning liquid B in the cleaning tank 1 is discharged through the discharge pipe 2, and the cleaning of the semiconductor substrate 7 with the cleaning liquid A and the cleaning liquid B is completed. When cleaning with various types of cleaning liquids, supply a cleaning liquid to the cleaning tank by providing a supply pipe for each cleaning liquid, discharge the liquid through the discharge pipe, and then supply the next cleaning liquid to perform cleaning sequentially. become.

FIG. 3 is a cross-sectional view showing the second method, and a cleaning method using three types of cleaning liquids will be described with reference to FIG.

Reference numerals 15, 16, and 17 denote cleaning tanks provided for each of the cleaning liquids. Supply valves 18, 19, and 20 are provided at the bottoms of the cleaning tanks, and the cleaning liquids C, D,
Supply pipes 21, 22, and 23 for supplying E to each cleaning tank are attached. A shelf 5 is provided at an intermediate portion in each cleaning tank at a position where the semiconductor substrate 7 placed on the substrate transporter 6 is below the level of the cleaning liquid.

In such a configuration, the cleaning tanks 15, 16, 17
Open the supply valves 18, 19, 20 respectively, and supply pipes 21, 22, 23
Supplies the cleaning liquids C, D, and E. Each cleaning liquid is filled in each cleaning tank more than the entire surface of the semiconductor substrate 7 is immersed. First wash tank
The semiconductor substrate 7 is placed on the 15 shelves 5 while being placed on the substrate transporter 6, and immersed in the cleaning liquid C for a predetermined time to perform cleaning. Thereafter, the semiconductor substrate 7 is pulled up from the cleaning tank 15 while being placed on the substrate transporter 6, placed on the shelf 5 of the next cleaning tank 16, and immersed in the cleaning liquid D to perform cleaning for a predetermined time. Further, the semiconductor substrate 7 is pulled up from the cleaning tank 16 while being placed on the substrate transporter 6, placed on the shelf 5 of the next cleaning tank 17, and immersed in the cleaning liquid E to perform cleaning for a predetermined time. Thereafter, the semiconductor substrate 7 is pulled up from the cleaning tank 17 while being placed on the substrate transporter 6, and the cleaning liquid C and the cleaning liquid D
The cleaning of the semiconductor substrate 7 with the cleaning liquid E is completed. The cleaning may be performed while always supplying a cleaning liquid as needed and overflowing the upper edge of the cleaning tank. In the case of cleaning using various types of cleaning liquids, a cleaning tank is provided for each cleaning liquid, and the like.
The washing tank is sequentially changed, and the washing is performed by immersing in the washing liquid.

In each of the conventional cleaning methods described above, when the cleaning liquid is transferred from one to the next, a part or all of the semiconductor substrate 7 comes into contact with the atmosphere once. Exposure of the semiconductor substrate 7 to the air causes an increase in adsorption of contamination from the air to the cleaned substrate surface. That is, dust and reaction products adhere. In addition, when the cleaning liquid is changed, the cleaning liquid moves on the surface of the semiconductor substrate. Therefore, depending on the condition of the substrate surface, the liquid-solid interface where the cleaning liquid remains on the substrate surface and the liquid-solid interface where the cleaning liquid does not remain are determined. Both the gas-solid interface are mixed and etching unevenness occurs in the mixed portion including the case where the gas-solid interface is immersed in the next cleaning liquid, and the occurrence of haze is observed. Further, even if the above measures are taken, the surface of the semiconductor substrate 7 moves on the surface of the cleaning liquid, that is, the gas-liquid interface, every time the cleaning liquid is changed. The problem remains that existing contaminants adhere to the substrate surface and contaminate it.

(Problems to be solved by the invention) The present invention has been made in view of the above situation,
The purpose is to clean the semiconductor substrate,
Since the substrate is not exposed to the air during cleaning and the level of the cleaning liquid does not pass through the substrate surface each time the cleaning liquid is changed, there is no haze, and there is little contaminant adhering. It is an object of the present invention to provide a method for cleaning a semiconductor substrate, which can realize an integrated semiconductor device.

[Means for Solving the Problems] In the method of cleaning a semiconductor substrate of the present invention with at least two or more types of cleaning liquids, the semiconductor substrate is placed in a cleaning tank so as to be below the level of the cleaning liquid. Stored, and also when switching from one cleaning liquid to another cleaning liquid and cleaning, the cleaning liquid is sequentially switched while continuously flowing so that the cleaning liquid always overflows and is discharged from the cleaning tank. The cleaning is performed while being held in the liquid.

(Operation) In the method of cleaning a semiconductor substrate formed as described above, the semiconductor substrate is housed in a cleaning tank so as to be below the level of the cleaning liquid, and each cleaning liquid is successively supplied to the semiconductor substrate in order to perform cleaning. Cleaning is performed without lifting the semiconductor substrate from the cleaning tank containing the cleaning liquid on the way. At this time, the continuously supplied cleaning liquid always overflows from the cleaning tank. For this reason, the semiconductor substrate does not come into contact with the air during cleaning, and the gas-liquid interface, which is the liquid level of the cleaning liquid, passes through the surface of the semiconductor substrate only when the semiconductor substrate is taken out after the cleaning. No contaminants are adhered to the surface.

(Embodiment) An embodiment of the present invention will be described below with reference to a front view in which main parts of FIG. 1 are cut away. Note that the same reference numerals are given to the same parts as those in the related art, and the description will be omitted.

Reference numeral 30 denotes a cleaning tank, and a gutter section 31 for forming a discharge path of the cleaning liquid overflowing and discharging from the cleaning tank 30 is provided all around the outer surface of the upper edge, and a supply section for forming a manifold section at the bottom. One end of the tube 32 is attached. One end of the supply pipe 32 is connected to a first supply source 35 for supplying, for example, pure water via a first supply valve 33 and a first flow rate controller 34. A first supply branch pipe 36 is provided at an intermediate portion on the valve 33 side.
A second supply branch 37 and a third supply branch 38 are attached at one end. Further, second, third, and fourth supply valves 39, 40, and 41 are provided at one ends of the first to third supply branch pipes 36 to 38, respectively.
, And second, third, and fourth flow controllers 42, 43, and 44, respectively, are connected to supply sources of respective chemicals such as hydrogen fluoride, hydrochloric acid, and hydrogen peroxide. 45 is a second source for supplying hydrogen fluoride; 46 is a third source for supplying hydrochloric acid;
Is a fourth source for supplying hydrogen peroxide.

In cleaning the semiconductor substrate 7 in such a configuration, first, the second to fourth supply valves 39 to 41 are closed, the first supply valve 33 is opened, and the first flow controller 34 is used. Pure water is supplied to the washing tank 30 so as to overflow while adjusting the flow rate. In this manner, the semiconductor substrate 7 placed on the substrate transporter 6 is placed on the shelf 5 of the cleaning tank 30 so that the entire surface thereof is immersed, and the semiconductor substrate 7 is cleaned with pure water. Subsequently, the second supply valve 39 is opened, and hydrogen fluoride is supplied from the second supply source 45 through the first supply branch pipe 36 to the supply pipe 32 through which pure water flows.
To be sent to Hydrogen fluoride is mixed with pure water while flowing through the supply pipe 32, diluted and supplied so as to overflow into the cleaning tank 30, and the supply amount of hydrogen fluoride is predetermined in the cleaning tank 30. The adjustment is performed by adjusting the second flow rate controller 42 so that the concentration of hydrogen fluoride is attained. After cleaning with hydrogen fluoride for a predetermined time, the second supply valve 39 is closed, and the cleaning tank 30 is filled with pure water only. Next, the third supply valve 40 is opened, and hydrochloric acid is supplied from the third supply source 46 to the supply pipe 32 through which pure water flows through the second supply branch pipe 37. Hydrochloric acid is diluted with pure water while flowing through the supply pipe 32, and supplied so as to overflow into the cleaning tank 30. , The third flow controller 43 is adjusted. After cleaning with hydrochloric acid for a predetermined time, the third supply valve 40 is closed, and the cleaning tank 30 is made to contain only pure water. Further, the fourth supply valve 41 is opened, and hydrogen peroxide is supplied from the fourth supply source 47 through the third supply branch pipe 38.
The water is supplied to a supply pipe 32 through which pure water flows. Hydrogen peroxide is diluted with pure water while flowing through the supply pipe 32, and is supplied so as to overflow into the cleaning tank 30.
Then, the fourth flow rate controller 44 is adjusted so that the concentration of hydrogen peroxide becomes a predetermined level. After cleaning with hydrogen peroxide for a predetermined time, the fourth supply valve 41 is closed, and the cleaning tank 30 is made to contain only pure water. Thereafter, the semiconductor substrate 7 is taken out from the cleaning tank 30 while being placed on the substrate transporter 6, and the entire cleaning is completed.
Incidentally, if necessary, pure water may be heated and supplied as hot water to the supply pipe 32, and the amount of each chemical solution added to the pure water is large,
When using a highly concentrated cleaning liquid, a screw-type agitator is installed inside the supply pipe 32 downstream of the attachment part of each supply branch pipe or at the bottom of the cleaning tank 30 to stir and promote mixing. You may.

By carrying out as described above, even when the cleaning is performed by transferring from one cleaning liquid to another cleaning liquid, the cleaning liquid is transferred while continuously flowing the cleaning liquid.
The cleaning liquid is not exposed to the atmosphere by drawing it out of the cleaning tank 30 or emptying the cleaning tank 30.Also, the cleaning liquid is continuously flowed so as to overflow from the cleaning tank, and the cleaning liquid is washed. The liquid level passes through the surface of the semiconductor substrate 7 only once when the semiconductor substrate 7 has been cleaned and finally removed from the cleaning tank 30.

Therefore, contamination (dust, reaction products, etc.) from the air on the cleaned semiconductor substrate surface is eliminated, and haze due to uneven etching does not occur. Further, the amount of contaminants present at the gas-liquid interface of the cleaning liquid on the substrate surface is reduced. In addition, the concentration of each chemical solution can be adjusted and changed during cleaning, it is possible to respond to the situation of the substrate surface, and the combination of flowing each chemical solution can be changed, so that cleaning with different specifications can be performed. it can.

In the above-described embodiment, the supply pipes are attached to the supply pipe 32 as a manifold portion, and the main mixing of each cleaning liquid is performed here. However, each supply branch pipe is directly attached to the bottom of the cleaning tank. At the bottom and mixing within this bottom. Further, the chemical solution is not limited to the above, and the use of pure water is not essential. Further, in the above, each cleaning liquid was made to be a mixture of pure water and each chemical liquid, and the next cleaning liquid was flowed after the pure water was flown in between. The next washing liquid may be flowed. Furthermore, the present invention can be carried out with appropriate changes without departing from the gist, for example, two or more kinds of chemical solutions may be mixed and used.

[Effects of the Invention] As is clear from the above description, the present invention stores a semiconductor substrate in a cleaning tank so as to be below the level of the cleaning liquid, and continuously discharges the cleaning liquid from the cleaning tank so as to always overflow. The semiconductor substrate is not exposed to the air during the cleaning process, and the surface level of the cleaning solution is changed each time the cleaning solution is changed. Since there is no passage, haze is not generated, and contaminants to be attached are reduced, so that a semiconductor substrate suitable for realizing a highly integrated semiconductor device can be provided.

[Brief description of the drawings]

FIG. 1 is a front view of an embodiment according to the present invention, FIG. 2 is a cross-sectional view for explaining a first conventional method, and FIG. 3 is a view for explaining a second conventional method. It is sectional drawing. 7 semiconductor substrate, 30 cleaning tank, 31 gutter part, 32 supply pipe, 35 first supply source, 45 second supply source, 46 third supply source , 47... A fourth source.

Claims (1)

(57) [Claims] 1. A method for cleaning a semiconductor substrate with at least two types of cleaning liquids, wherein the semiconductor substrate is contained in a cleaning tank so as to be below the level of the cleaning liquid, and the semiconductor substrate is converted from one cleaning liquid to another cleaning liquid. When the cleaning is carried out, the respective cleaning liquids are sequentially switched while continuously flowing so that the cleaning liquid always overflows and is discharged from the cleaning tank, and the cleaning is performed so that the semiconductor substrate is always kept in the liquid. A method for cleaning a semiconductor substrate, comprising: